Rusty Russell wrote:
On Sun, 2007-06-17 at 17:25 +0300, Avi Kivity wrote:
Rusty Russell wrote:
+ /* Set up for reply. */
+ vblk->sg[0].page = virt_to_page(&vbr->in_hdr);
+ vblk->sg[0].offset = offset_in_page(&vbr->in_hdr);
+ vblk->sg[0].length = sizeof(vbr->in_hdr);
+ num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);
+ vbr->out_hdr.id = vblk->vdev->ops->add_inbuf(vblk->vdev, vblk->sg,
+ 1+num, vbr);
+ if (IS_ERR_VALUE(vbr->out_hdr.id))
+ goto full;
+
+ vblk->sg[0].page = virt_to_page(&vbr->out_hdr);
+ vblk->sg[0].offset = offset_in_page(&vbr->out_hdr);
+ vblk->sg[0].length = sizeof(vbr->out_hdr);
+
+ vbr->out_id = vblk->vdev->ops->add_outbuf(vblk->vdev, vblk->sg, 1,
+ vbr);
This strikes me as wasteful. Why not set up a single descriptor which
contains both placement and the data itself?
We could actually do this for write, but not for read (where the length
& sector need to be sent to other end, and the data comes from other
end).
So you map the first sg entry for output, and the rest for input.
Less pretty, but more efficient.
--
error compiling committee.c: too many arguments to function
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